﻿#pragma once
#include <iostream>
#include <vector>
#include <unordered_map>
#include <map>
#include <algorithm>
#include <time.h>
#include <Windows.h>
#include <assert.h>
#include <thread>
#include <mutex>
#include <atomic>

// 自由链表的哈希桶跟对象大小的映射关系
// 小于等于MAX_BYTES，就找thread cache申请
// 大于MAX_BYTES，就直接找page cache或者系统堆申请
static const size_t MAX_BYTES = 256 * 1024;
// thread cache 和 central cache自由链表哈希桶的表大小
static const size_t NFREELIST = 208;
// page cache 管理span list哈希表⼤⼩
static const size_t NPAGES = 129;
// 页大小转换偏移，即一页定义为2^13，也就是8KB
static const size_t PAGE_SHIFT = 13;

// ⻚编号类型，32位下是4byte类型，64位下是8byte类型
#ifdef _WIN64
typedef unsigned long long PageID;
#elif _WIN32
typedef size_t PageID;
#endif

// 直接去堆上按⻚申请空间
inline static void* SystemAlloc(size_t kpage)
{
#ifdef _WIN32
	void* ptr = VirtualAlloc(0, kpage * (1 << 12), MEM_COMMIT | MEM_RESERVE,PAGE_READWRITE);
#else
	// linux下brk mmap等
#endif
	if (ptr == nullptr)
	{
		throw std::bad_alloc();
	}
	return ptr;
}

inline static void SystemFree(void* ptr)
{
#ifdef _WIN32
	VirtualFree(ptr, 0, MEM_RELEASE);
#else
	// sbrk unmmap等
#endif
}


// 获取内存对象中存储的头4 or 8字节值，即链接的下⼀个对象的地址
static void*& NextObj(void* obj)
{
	return *(void**)obj;
}
// 管理切分好的小对象的自由链表
class FreeList
{
public:
	void Push(void* obj)
	{
		assert(obj);
		// 头插
		//*(void**)obj = _freeList;
		NextObj(obj) = _freeList;
		_freeList = obj;
		_size++;
	}

	void* Pop()
	{
		assert(_freeList);
		// 头删
		void* obj = _freeList;
		_freeList = NextObj(obj);
		_size--;

		return obj;
	}

	void PushRange(void* start, void* end,size_t n)
	{
		NextObj(end) = _freeList;
		_freeList = start;

		_size += n;
	}

	void PopRange(void*& start, void*& end, size_t n)
	{
		assert(n <= _size);
		start = _freeList;
		end = start;

		for (size_t i = 0; i < n - 1; i++)
		{
			end = NextObj(end);
		}

		_freeList = NextObj(end);
		NextObj(end) = nullptr;
		_size -= n;
	}

	bool Empty()
	{
		return _freeList == nullptr;
	}

	size_t& MaxSize()
	{
		return _maxSize;
	}

	size_t Size()
	{
		return _size;
	}

private:
	void* _freeList = nullptr;
	size_t _maxSize = 1;
	size_t _size = 0;
};

// 管理对齐和映射等关系
class SizeClass
{
public:
	// 整体控制在最多10%左右的内存碎片浪费
	// [1,128]					8byte对⻬		freelist[0,16)
	// [128+1,1024]				16byte对⻬		freelist[16,72)
	// [1024+1,8*1024]			128byte对⻬		freelist[72,128)
	// [8*1024+1,64*1024]		1024byte对⻬		freelist[128,184)
	// [64*1024+1,256*1024]		8*1024byte对⻬	freelist[184,208)
	
	/*size_t _RoundUp(size_t bytes, size_t align)
	{
		size_t alignSize;
		if (bytes % align != 0)
		{
			alignSize = (bytes / align + 1) * align;
		}
		else
		{
			alignSize = bytes;
		}
		return alignSize;
	}*/
	static inline size_t _RoundUp(size_t bytes, size_t align)
	{
		return ((bytes+align - 1) & ~(align - 1));
	}

	// 对齐大小计算
	static inline size_t RoundUp(size_t bytes)
	{
		if (bytes <= 128)
		{
			return _RoundUp(bytes, 8);
		}
		else if (bytes <= 1024)
		{
			return _RoundUp(bytes, 16);
		}
		else if (bytes <= 8 * 1024)
		{
			return _RoundUp(bytes, 128);
		}
		else if (bytes <= 64 * 1024)
		{
			return _RoundUp(bytes, 1024);
		}
		else if (bytes <= 256 * 1024)
		{
			return _RoundUp(bytes, 8 * 1024);
		}
		else
		{
			return _RoundUp(bytes, 1 << PAGE_SHIFT);
		}
	}

	/*static inline size_t _Index(size_t bytes, size_t align_shift)
	{
		if (bytes % align_shift == 0)
		{
			return bytes / align_shift - 1;
		}
		else
		{
			return bytes / align_shift;
		}
	}*/
	static inline size_t _Index(size_t bytes, size_t align_shift)
	{
		return ((bytes + (static_cast<unsigned long long>(1) << align_shift) - 1) >> align_shift) - 1;
	}

	// 计算映射的哪一个自由链表桶
	static inline size_t Index(size_t bytes)
	{
		assert(bytes <= MAX_BYTES);

		// 每个区间有多少个链
		static int group_array[4] = { 16,56,56,56 };
		if (bytes <= 128)
		{
			return _Index(bytes, 3);
		}
		else if (bytes <= 1024)
		{
			return _Index(bytes - 128, 4) + group_array[0];
		}
		else if (bytes <= 8 * 1024)
		{
			return _Index(bytes - 1024, 7) + group_array[1] + group_array[0];
		}
		else if (bytes <= 64 * 1024)
		{
			return _Index(bytes - 8 * 1024, 10) + group_array[2] + group_array[1] + group_array[0];
		}
		else if (bytes <= 256 * 1024)
		{
			return _Index(bytes - 64 * 1024, 13) + group_array[3] + group_array[2] + group_array[1] + group_array[0];
		}
		else
		{
			assert(false);
		}
		return -1;
	}

	// ⼀次thread cache从中⼼缓存获取多少个
	static size_t NumMoveSize(size_t size)
	{
		assert(size > 0);

		// [2, 512]，⼀次批量移动多少个对象的(慢启动)上限值
		// ⼩对象⼀次批量上限⾼
		// ⼩对象⼀次批量上限低
		size_t num = MAX_BYTES / size;
		if (num < 2)
		{
			num = 2;
		}
		if (num > 512)
		{
			num = 512;
		}
		return num;
	}

	// 计算⼀次向系统获取⼏个⻚
	// 单个对象 8byte
	 // ...
	// 单个对象 256KB
	static size_t NumMovePage(size_t size)
	{
		size_t num = NumMoveSize(size);
		size_t npage = num * size;

		npage >>= PAGE_SHIFT;
		if (npage == 0)
		{
			npage = 1;
		}
		return npage;
	}
};

// Span管理一个跨度的大块内存
// 管理以页为单位的大块内存
// 管理多个连续页大块内存跨度结构
struct Span
{
	PageID _pageId = 0; // ⼤块内存起始⻚的⻚号
	size_t _n = 0;      // ⻚的数量

	Span* _next = nullptr;    // 双向链表的结构
	Span* _prev = nullptr;

	size_t _objSize = 0;  // 切好的小对象的大小
	size_t _useCount = 0; // 切好小块内存，被分配给thread cache的计数
	void* _freeList = nullptr; // 切好的小块内存的自由链表

	bool _isUse = false; // 是否在被使用
};

// 带头双向循环链表
class SpanList
{
public:
	SpanList()
	{
		_head = new Span;
		_head->_next = _head;
		_head->_prev = _head;
	}

	Span* Begin()
	{
		return _head->_next;
	}

	Span* End()
	{
		return _head;
	}

	bool Empty()
	{
		return _head->_next == _head;
	}

	void PushFront(Span* span)
	{
		Insert(Begin(), span);
	}

	Span* PopFront()
	{
		Span* front = _head->_next;
		Erase(front);
		return front;
	}

	void Insert(Span* pos, Span* newSpan)
	{
		assert(pos);
		assert(newSpan);

		Span* prev = pos->_prev;
		prev->_next = newSpan;
		newSpan->_prev = prev;
		newSpan->_next = pos;
		pos->_prev = newSpan;
	}

	void Erase(Span* pos)
	{
		assert(pos);
		assert(pos != _head);

		Span* prev = pos->_prev;
		Span* next = pos->_next;

		prev->_next = next;
		next->_prev = prev;
	}

private:
	Span* _head;
public:
	std::mutex _mtx; // 桶锁
};